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Immunogene Therapy of Breast Cancer
Background: Anti-cancer T cells generated by genetic modification of patient lymphocytes are a promising means of specific, effective cancer therapy. We have demonstrated that adoptive transfer of CD8+ T cells armed with an enhanced gene results in long-term survival of approximately 50% of mice with experimental lung metastases. The enhanced gene encoded a cell surface receptor composed of extracellular single-chain antibody specific for the breast cancer associated antigen, erbB-2, linked to the intracellular signalling domains of CD28 and TCR-zeta in a single molecule. Recently, we achieved an improvement in therapy by the inclusion of specific CD4+ helper T cells in the treatment regimen resulting in survival of 100% of mice. In our most recent experiments we have demonstrated that a combination of surgery and adoptively transferred gene-modified T cells can result in the long-term survival of mice with widespread spontaneous metastatic breast cancer. This form of therapy was far superior to that afforded by the conventional chemotherapeutic agents Doxorubicin and 5-Fluorouracil in this model. Based on these results in mice, we now wish to develop a gene suitable for the treatment of patients with lung metastases and/or minimal disseminated metastases, while also further investigating our approach to enhance its efficacy against late-stage metastatic disease.
Objective: To develop an effective, specific therapy for breast cancer using genetically enhanced T lymphocytes.
Aims: (1) Preclinical evaluation of human T cells gene-modified with a humanized anti-LeY chimeric receptor.
(2) Further optimization of T cell treatment of advanced breast cancer in mice.
Study design: In Aim 1, human T cells will be gene-modified with a humanized chimeric receptor specific for Lewis Y (LeY) that is a carbohydrate antigen over-expressed on 70% of breast cancers. Several vector systems will be compared for their ability to impart maximum transduction of T cells. In addition, a “suicide gene” component will be tested that will enable the elimination of LeY-reactive T cells in patients in the event of an autoimmune reaction or other complications. Transduced T cells will be fully characterized for expression and function of the anti-LeY receptor in vitro. Function against tumor cells will be determined by cytokine secretion, cytotoxicity and proliferation assays. In vivo anti-tumor activity of gene-modified human and mouse T cells will then be determined in mice against the breast cancer cell lines, MCF-7 and MDA-MB-231. In Aim 2, investigations will be performed to gain mechanistic insight into the enhanced anti-tumor effect observed in mice when large numbers of tumor-reactive CD4+ T cells are included in the therapeutic regimen. CD4+ T cells from a range of mice deficient in genes including cytokines and cytotoxic molecules will be used against the spontaneously metastatic mouse breast cancer cell line, 4T1. In addition, the effect of CD4+ T cells on CD8+ T cell survival and localization to tumor will be determined.
Potential outcomes and benefits of the research: The genetic reagent designed and characterized in Aim 1 will eventually be used in a Phase I clinical trial of advanced cancer patients and then if successful in an adjuvant setting following surgical removal of primary breast tumor. Investigations into tumor-reactive CD4+ helper T cells in Aim 2 will yield important mechanistic insight into the observed enhanced anti-tumor effect afforded by the inclusion of these cells in the treatment regimen. These insights will be important in the further optimization of the approach for the treatment of more advanced disease.
We propose to use the body’s own immune system against breast cancer. The immune system has many millions of white blood cells. These cells reside in lymph nodes around the body, and circulate through the bloodstream in search of diseased tissue. There are several types of white blood cell, one type of which is called a T cell. T cells are particularly powerful cells that are the linchpin of the immune system, and hence the focus of this project.
T cells have several attributes that make them very attractive as weapons against cancer. Firstly, they are extremely specific. They are virtually the ultimate “smart” cellular weapons, able to target and destroy diseased tissue while leaving normal tissue unharmed. Therefore, therapy using T cells should have no toxic side effects. Secondly, T cells are particularly powerful. They are able to eliminate diseased tissue by recognizing it, attaching to it, and destroying it by delivering a payload of biochemicals. In addition, T cells can send messages to attract other white blood cells to the fray. Thirdly, T cells are systemic; they are able to penetrate all parts of the body.
However, natural T cells of most breast cancer patients are unable to recognize cancer, and therefore powerless against it. The therapy we are developing in this project involves genetic engineering of patient T cells with a gene that enables recognition and destruction of cancer. We call the gene an “immunogene” because it is made up of molecules of the immune system. An immunogene can empower the immune system to react against cancer. The clinical use would involve taking a sample of T cells from the blood of a patient and inserting the immunogene into the T cells in the laboratory. The modified T cells would then be returned to the patient as a transfusion.
In earlier experiments, we used a “first generation” immunogene in T cells and found that they had a modest effect against cancer in mice. We then went on to use a “second generation” gene and found that about 50% of mice suffering from lung metastases could survive long-term. In very recent studies we have achieved even better therapy against lung metastases by adding a specialist type of T cell called a helper CD4 cell. One hundred percent of mice can now be cured of lung metastases using these cells along with other T cells. Mice treated in this fashion have survived over six months with no signs of cancer, and are expected to have a normal 2 years life span. The most exciting developments have happened in the past 3 months, where we have used immunogene-modified T cells to successfully treat mice with widespread metastatic breast cancer of the lung, liver and bones. We now have a promising therapy to offer breast cancer patients, and the preclinical work-up of this approach makes up Aim 1 of this funding proposal.
The project proposed for funding by The Susan G. Komen Breast Cancer Foundation will build on basic research funded by the Foundation in a previous round. In the current application, we wish to take the immunogene and get it ready for use in patients by making all the components human and safe. In addition, we propose to continue efforts to further develop the effectiveness of the approach in mouse models. The aims are therefore: (1) Prepare a human immunogene for patient therapy; (2) Further investigate the use of CD4 helper T cells in the mouse.
Using these original and innovative approaches, our team is at the forefront of efforts to genetically boost the immune system against cancer. We anticipate that the proposed studies will lead to a product for use as a novel therapy. The studies will also give us a clearer picture of the requirements for an effective response against tumor, and bring us closer to helping all those afflicted by breast cancer.